<!DOCTYPE html>
<html>
<head>
<style>
fieldset {
  display: inline; background: rgba(255, 255, 0, 0.7); color: black;
}
div { background: green; }
div#one { float: left; }
</style>
</head>
<body>
  <form>
    <fieldset>
      <div id="one">I should be black text on a green background</div>
    </fieldset>
    <fieldset>
      <div>I should be black text on a green background</div>
    </fieldset>
  </form>
</body>
</html>
